The present invention relates to syndiotactic vinylaromatic homopolymers and copolymers having a high melt flow and a method for the manufacture thereof. It is previously known in the art to prepare vinylaromatic polymers having a high degree of syndiotacticity.
In U.S. Pat. No. 5,037,907 and U.S. Pat. No. 5,254,647 suitable reactor designs, catalysts and processing conditions for preparing syndiotactic vinylaromatic polymers are taught. In U.S. Pat. No. 4,990,580, the use of hydrogen at a partial pressure within the range of 0.01 to 50 kg/cm2 (1 to 5000 kPa) in order to control the molecular weight of the resulting syndiotactic vinylaromatic polymer product was taught. In U.S. Pat. No. 5,824,753, syndiotactic polymers of vinylaromatic monomers were prepared by contacting one or more vinylaromatic monomers and one or more catalyst compositions comprising a titanium based metal complex, a trialkylaluminum compound and hydrogen in a partial pressure up to 5 MPa, suitably 50 to 100 kPa In U.S. Pat. No. 5,468,818, improved catalyst efficiency is obtained in a polymerization process for preparing syndiotactic polymers of vinylaromatic monomers comprising contacting one or more vinylaromatic monomers and one or more catalyst compositions comprising a pentamethylcyclopentadienyltitanium based metal complex capable of preparing syndiotactic vinylaromatic polymers, a trialkylaluminum compound and a hydrogen partial pressure from 10 to 45 kPa. was disclosed.